What we've learnt from natural disasters

Recently our local region has been subject to floods, tropical cyclones, bushfires and earthquakes.  Unfortunately these disasters have resulted in casualties and we're extremely sensitive to this and express our deepest sympathies to those affected by the disasters.

However it is critical that we learn from these disasters so that we can design and build structures that will better survive in the future.  By doing this we help make communities more resilient to these events.

Floods

Australia has been subject to the biggest series of floods that it has seen for many years.  These were generally associated with an El Nino weather pattern that raised the sea temperature.

Steel frames have performed well in the floods and proved quick and easy to repair.  In this issue's Case Study on the Dubbo floods, we describe Harnett Homes in Dubbo's experiences of flooding and consequential actions to fix the transportable homes that were damaged.

The above average rain fall and associated flooding and increased humidity has also added to the termite risks as termites like damp conditions.  Floods may have caused the termite protection systems to be comprised by:

• washing the termite treatment out of the soil
• washing mud over termite barriers allowing the termites to enter the building unobserved
• dissolving the treatment - most timber termite treatments are water soluble and will be made ineffective when immersed in water.

As illustrated in the Case Study the plaster can be removed from the steel frame, the mud washed out of the cavity and the plaster replaced over a very short time period.  Whereas the timber frame needs to be dried out so that the moisture content drops below 16% before the wall lining can be replaced.  The repair or replacement of appliances, plumbing, electrical, carpets and painting should not occur until the building fabric has dried out.  (Reference: Building Services Authority (BSA) Contractors Guide for Restoring a House after Flood.)

Charlton, situated on the Avoca River in North Western Victoria, was another town subjected to major floods in September 2010 and again in January 2011.

The oldest part of the Charlton hospital was constructed of double brick in 1965 and in the January floods was inundated with approximately half a metre of water.  The flood water caught in the brick wall cavity and became susceptible to bacteria breeding.  Tests were required to determine the toxicity of the water and it was questionable whether the building could be made clean enough to operate as a hospital again.  Since then the mould has grown rapidly on the walls and it is now planned to rebuild a new hospital for Charlton.